1. Field of the Invention
The present invention relates to a flywheel power source device which stores kinetic energy by rotating a flywheel at high speed and reconverts the stored kinetic energy of the flywheel to electric energy when necessary.
2. Description of the Related Art
The present applicant has applied a flywheel power source device A which eliminates work of precise leveling when it is installed and is highly resistant to lateral swing (Japanese Patent Application Unexamined Publication No. HEI 7(1995)-322533). This flywheel power source device A (hereinafter referred to as a conventional device A) will be described with reference to FIG. 2.
A flywheel B has a main body part C shaped like an inverted cup and a rotary shaft D provided at the center of the main body part C, the bottom end of the rotary shaft D being rotatably fitted in a pivot bearing F provided on a casing E and the central top of the flywheel B being rotatably fitted on a bearing H provided on the casing E. The bearing H has a structure in which a circular recessed part J of the flywheel B is fitted on a short shaft I of the casing E side, wherein there is a small gap between the short shaft I (to be exact, a ball bearing Ix) and the circular recessed part J.
The flywheel B is provided with a rotor M having an iron core K which is mounted on the inner peripheral surface of the main body part C and is sandwiched by end rings L, L. On the other hand, a stator P is mounted on a bottom wall N of the casing E in such a way that it is opposed to the rotor M of the flywheel B. The stator P includes a fixed base part Q projected from the bottom wall N, an iron core R mounted around the base part Q, and a coil S.
In the conventional device A described above, if voltage is applied to the coil S of the stator P by an external power source, a rotational force is generated by magnetic action caused on the same principle as that of an electric motor to rotate the flywheel B. By rotating the flywheel B at high speed, electric energy is converted to kinetic energy and is stored as the kinetic energy. In this respect, while the flywheel B is being rotated, it is rotated like a top on one point of the pivot bearing F and the circular recessed part J is not in contact with the short shaft I, which significantly reduces the mechanical loss of the flywheel B. Next, when power supply to the coil S is stopped owing to power failure or the like, the kinetic energy of the flywheel B is reconverted to the electric energy on the same principle as a generator and the electric energy is supplied to the external load.
That is to say, in the above-mentioned conventional device A, the rotational fulcrum at the bottom end of the rotary shaft D is aligned with the center of gravity G of the flywheel B, so as to prevent the precession of the flywheel B. (The precession means that the upper end of the rotary shaft D swings along arcs around the rotational center at the bottom end of the rotary shaft D on the principle of a top.) In this regard, if the flywheel B starts the precession, the circular recessed part J is brought into contact with the ball bearing Ix of the short shaft I to increase the mechanical loss, which aggravates efficiency, shortens its life and makes noises while being operated. As the result, the performance of the flywheel power source device is substantially reduced.
The above-mentioned conventional device A is stable in a state in which the flywheel B rotates at high speed and does not start the precession even if it is placed on a slant position or it is swung laterally, and hence solves almost all the problems caused by the precession of the flywheel B. However, it has been found that under special conditions, that is, when the flywheel B in a stop state is started by large voltage, the flywheel B starts the precession and the rotary shaft D is held inclined (the circular recessed part J is held in contact with the ball bearing Ix of the short shaft I) and cannot be returned to the original state. Yet, even in the conventional device A, if the number of revolutions of the flywheel B is gradually increased by applying reduced voltage thereto, the above-mentioned problems do not arise.
In order to find the cause of the problem described above, the conventional device A has been analyzed and it has been found that, as shown in FIG. 2, there was a deviation Z between the center line X of the iron core K of the rotor M on the flywheel B side or the center line Y of the iron core R of the stator P on the casing E side (the center line Y and the center line X usually overlap one another.) and the rotational fulcrum at the bottom end of the rotary shaft D. The deviation Z generates force for inclining the flywheel B around the rotational fulcrum under the special conditions described above.
That is, when the flywheel B is rotated, magnetic attractive forces are applied to the iron cores K, R and it is considered that the resultant force of the magnetic attractive forces is applied to the center lines X, Y of the iron cores K, R. If there is a deviation Z between the center lines X, Y of the iron cores K, R and the rotational fulcrum of the flywheel B, as described above, moment in the direction inclining the flywheel B around the rotational fulcrum acts on the flywheel B in proportion to the magnitude of the magnetic attractive force and the magnitude of the deviation Z. Since the magnetic attractive forces of the iron cores K, R increase in proportion to voltage, when the flywheel B is started by large voltage, the effect of the moment acting on the flywheel B increases. As the result, the flywheel B is being rotated as it is inclined.